The present invention relates to an apparatus for melt spinning multifilament yarns from fiber-forming polymers at wind-up speeds of at least 2,000 m/min. The apparatus includes a spinnerette, a cooling means for solidifying the filaments, a convergence element for the filaments and a wind-up means. The apparatus also includes an essentially vertical spinline at least between the spinnerette and the first convergence element. The invention also relates to the use of this apparatus for manufacturing polyester filament yarns.
In the manufacture of multifilament yarns from fiber-forming polymers, manufacturing costs are crucially affected by the wind-up speed. Wind-up speeds of 3,500 to about 5,000 m/min are common today, while wind-up speeds of more than 5,000 m/min to about 12,000 m/min are also known. At these high wind-up speeds, in particular at wind-up speeds above 5,000 m/min, it is known from prior art manufacturing processes that the design of the apparatus used to perform the process plays an ever greater part in the manufacture of multifilament yarns, whereas purely process features are becoming increasingly less significant.
For instance, EP-A-56,963 describes a process for manufacturing a polyester fiber using a wind-up speed of at least 5,000 m/min, where the extruded filaments are initially guided through a heating zone at least 50 mm in length and then directly into a suction device before they are wound up. As is discernible from the drawing, the apparatus described for carrying out this process has a notably simple design.
Further simplification of this known apparatus is revealed in EP-A-95,712, where the heating zone is initially followed by a cooling part for solidifying filaments and then by a convergence element for the filaments, after which the multifilament yarn is wound up. Essential parts of this apparatus are the heating zone below the spinnerette, the location for bundling the filaments and the wind-up speed of 7,000 m/min or more. A similar apparatus is described in EP-A-117,215, where not only the location for converging the filaments but also the distance between the spinnerette and the wind-up means are specified as essential features.
Although the descriptions of the aforementioned structural elements of the apparatus mention that a cooling part is necessary for solidifying the filaments, they do not provide any disclosure concerning the design of the cooling part.
EP-A-244,216 observes, in relation to the design of the cooling means, that the cooling air should be supplied under controlled conditions radially from out to in via a wire mesh cylinder. This apparatus additionally requires a sharp reduction in the exit cross-section of the wire mesh cylinder to a narrow tube, causing the start-up of spinning to be very complicated.
In WO 90/02222, the filament yarns are spun into a closed spin chamber. If this spin chamber is used as cooling means, cooling air is sucked off via an injector. To start up spinning, it is initially necessary to remove the injector, similarly causing the start-up of spinning to be very complicated.